// Copyright (C) Kumo inc. and its affiliates.
// Author: Jeff.li lijippy@163.com
// All rights reserved.
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
#pragma once

#include <pollux/common/hash_bit_range.h>
#include <pollux/exec/vector_hasher.h>
#include <pollux/core/plan_node.h>

namespace kumo::pollux::exec {
    /// Calculates partition number for each row of the specified vector using a
    /// hash function. The constructor with hashBitRange parameter requires both
    /// hashBitRange and keyChannels to be non-empty. The constructor with
    /// numPartitions allows the keyChannels argument to be empty. If keyChannels is
    /// empty, then the resulting partition number of partition() will always be
    /// zero.
    class HashPartitionFunction : public core::PartitionFunction {
    public:
        HashPartitionFunction(
            bool localExchange,
            int numPartitions,
            const RowTypePtr &inputType,
            const std::vector<column_index_t> &keyChannels,
            const std::vector<VectorPtr> &constValues = {});

        HashPartitionFunction(
            const HashBitRange &hashBitRange,
            const RowTypePtr &inputType,
            const std::vector<column_index_t> &keyChannels,
            const std::vector<VectorPtr> &constValues = {});

        ~HashPartitionFunction() override = default;

        std::optional<uint32_t> partition(
            const RowVector &input,
            std::vector<uint32_t> &partitions) override;

        int numPartitions() const {
            return numPartitions_;
        }

    private:
        void init(
            const RowTypePtr &inputType,
            const std::vector<column_index_t> &keyChannels,
            const std::vector<VectorPtr> &constValues);

        const bool localExchange_;
        const int numPartitions_;
        const std::optional<HashBitRange> hashBitRange_ = std::nullopt;
        std::vector<std::unique_ptr<VectorHasher> > hashers_;

        // Reusable memory.
        SelectivityVector rows_;
        raw_vector<uint64_t> hashes_;
    };

    /// Factory class to create HashPartitionFunction
    /// 'keyChannels' stores the index of keys to partition on, if the key is a
    /// constant, use index 'kConstantChannel' to indicate so and store the constant
    /// value as a base vector in 'constValues'
    /// The 'constValues' size is less than or equal to 'keyChannels' size
    class HashPartitionFunctionSpec : public core::PartitionFunctionSpec {
    public:
        HashPartitionFunctionSpec(
            RowTypePtr inputType,
            std::vector<column_index_t> keyChannels,
            std::vector<VectorPtr> constValues = {})
            : inputType_{std::move(inputType)},
              keyChannels_{std::move(keyChannels)},
              constValues_{std::move(constValues)} {
        }

        std::unique_ptr<core::PartitionFunction> create(
            int numPartitions,
            bool localExchange) const override;

        std::string toString() const override;

        melon::Dynamic serialize() const override;

        static core::PartitionFunctionSpecPtr deserialize(
            const melon::Dynamic &obj,
            void *context);

    private:
        const RowTypePtr inputType_;
        const std::vector<column_index_t> keyChannels_;
        const std::vector<VectorPtr> constValues_;
    };
} // namespace kumo::pollux::exec
